The present invention relates to a transmission medium, and more particularly, to a low cross talk electrical signal transmission medium.
The United States Federal Communications Commission (FCC) has adopted standards for electrical connectors used in the telecommunications industry to ensure intermateability. The most commonly utilized electrical connector is a modular plug and jack. The plug is typically terminated to a cable having a plurality of parallel conductors that are paired to form a signal loop, and the jack is commonly mounted to a panel or a printed circuit board connected to a communications network. As the modular plugs are utilized more frequently in high frequency data and communication applications, interference or cross talk that arises in adjacent and parallel contacts of the jack, and to a lesser degree in the plug, has become a problem in the industry. When an electrical signal of a given frequency is applied to a pair of conductors, an unequal portion of signal energy is transmitted to the individual conductors of an adjacent pair by each conductor of the signal pair. This transmission is primarily due to capacitive and inductive couplings between adjacent conductors being substantially higher than couplings of the other conductor of the signal pair, resulting in cross talk. Cross talk is further increased when both conductors of the signal pair are placed adjacent to and outside of opposing conductors of the other signal pair. The magnitude of the cross talk is effected by such factors as the positioning of the conductors, the distance between adjacent conductors and the dielectric material between the conductors.
It has been found that cross talk coupling induced by the plug and jack interface can be reduced by shifting the placement of the conductors after they exit the jack so as to induce signals of opposite phase to those which were induced inside the plug and jack. To decrease cross talk, the conductors that form both pairs should be routed in a pattern that is opposite in polarity to the pattern that produces cross talk in the jack and plug. One such routing method is disclosed in U.S. Pat. No. 5,299,956 and U.S. Pat. No. 5,310,363 issued to Brownell et al. Brownell et al. teaches a low cross talk transmission assembly comprising an electrical connector having a first and second conductor forming a first signal pair and a third and fourth conductor forming a second signal pair. The first and second conductors are positioned adjacent and parallel to each other. The third conductor is positioned adjacent and parallel to the first conductor, and the fourth conductor is positioned adjacent and parallel to the second conductor. Because this arrangement induces cross talk from one signal pair to another signal pair when signals are applied to either one of the pairs, the third conductor is routed adjacent to and parallel to the second conductor and away from the first conductor, and the fourth conductor is routed adjacent and parallel to the first conductor and away from the second conductor. This new path configuration reduces a substantial amount of cross talk induced in the first configuration.
An alternative solution to the cross talk problem is disclosed in U.S. Pat. No. 5,488,201 issued to Liu. In Liu a first end of a first conductor and a first end of a third conductor are folded into bends that are mutually inserted into each other and alternately arranged. Also, a first end of a second conductor and a first end of a fourth conductor are folded into bends that are mutually inserted into each other and alternately arranged. The alternating arrangement of the first and third conductors and the second and fourth conductors reduces the amount of cross talk between the conductors by forming a mutually corresponding capacitive arrangement for restoring electrical balance of the conductive pairs. This design, however, is intricate and requires complex configurations of the conductors to decrease the amount of cross talk. Further, the configurations are predisposed and therefore can not be manipulated to change impedance without manufacturing additional products having additional configurations.
It is therefore desirable to develop a less intricate design that may be easily manipulated to change impedance for partial cancellation of cross talk induced into a signal carrying cable pair by modular jacks and plugs, or other input/output signal connectors, while maintaining proper longitudinal balance and characteristics within the connector system.
This invention relates to a low cross talk electrical signal transmission assembly comprising a signal transmission medium having a first signal pair and a second signal pair. The first signal pair having a first conductor and a second conductor. The second signal pair having a third conductor and a fourth conductor. Each conductor is attached to a corresponding input signal. A first compensation line is attached to the first input signal, and a second compensation line is attached to the third input signal. The first compensation line and the second compensation line are intertwined to create a first compensation line assembly having capacitive and inductive coupling. A third compensation line is attached to the fourth input signal, and a fourth compensation line is attached to the second input signal. The fourth compensation line and the third compensation line are intertwined to create a second compensation line assembly with capacitive and inductive coupling.